The Spanish word 'flechazo' comes from combining the word 'flecha' (meaning 'arrow') with the suffix '-azo', which indicates a forceful impact or augmentative meaning. The word 'flecha' itself can be traced back through Old French 'flèche' (arrow) to the Frankish word 'fliukka', meaning 'that which flies'.

Interestingly, 'flechazo' has developed two main meanings in Spanish: the literal meaning of 'arrow strike' and the figurative meaning of 'love at first sight'. This metaphorical extension likely comes from the idea of Cupid's arrow striking someone's heart, causing immediate love - a common cultural concept that exists in many European languages.

The simpler and more common Spanish word 'flecha' (arrow) is directly related to 'flechazo'. While 'flecha' refers to the physical arrow itself, adding the '-azo' suffix transforms it into the more specific concept of an arrow's strike or impact. This same suffix '-azo' appears in many Spanish words to indicate a forceful hit or dramatic action, such as in 'puñetazo' (punch) or 'portazo' (door slam).

While English doesn't have any direct cognates from the Frankish 'fliukka', we can see a semantic connection with words like 'flight' and 'fly', which share the core concept of movement through the air. The English word 'fletcher' (someone who makes arrows) comes from the same French word 'flèche' that gave Spanish its word 'flecha', though 'fletcher' is now mainly encountered as a surname.